Screens used in direct screen printing are typically made using a photographic process to create the desired image on the screen. Therefore the screen and its associated frame must be accurately located when mounted on the printing apparatus to assure proper placement of the printed image onto the garment which is held on the pallet of the apparatus. The screen frame must be registered or positioned in lateral, vertical and longitudinal directions relative to the pallet and the material mounted thereon to assure quality of the printing process. When more than one color is necessary, the precise registration or positioning becomes even more critical. Such screens are removably mounted to a printing head which forms a portion of the printing apparatus.
Screen printing has grown over the past several decades into a very high volume business. One of the larger segments of this industry requires the printing of numerals upon athletic shirts and jerseys for high school, college, professional and amateur athletic teams as well as for casual wear sport jerseys and T-shirts.
Most athletic jerseys and shirts include numerals on the back and front. The more elaborate and expensive jerseys include numbers on the sleeves or shoulders. In many applications, a two color design is required wherein the primary numeral is bordered in a second color. Typically the front, back and sleeve numerals are of different sizes which require three separate screen designs for each numeral used.
Prior to the present invention, athletic shirt manufactureres were required to have a stock of approximately 100 silk screens including the frame, to represent the numerals 0 to 99 for each color and each size to be used. Another 100 screens in each size were required for a two color numeral printing. Therefore shirts or jerseys having two-color front and rear numerals required a total of 400 individual printing screens. If sleeve or shoulder numerals are included, an additional 200 screens were needed.
Further, after each numeral has been printed, each screen must be removed and another screen positioned and fixed onto the screen printing head assembly which lies above the pallet upon which the workpiece garment is placed. On conventional apparatus, this procedure required the user to loosen set screw type fastening devices, remove the screen, replace the new screen and accurately re-position the new screen by manual eye alignment prior to re-tightening the screw-type fastening devices.
In two-color processes, the precise placement or registration of the first and second color screens is imperative to assure that the outline secondary color is properly printed along the outer borders of the primary numeral color in the desired alignment.
The above procedure represented a cumbersome technique and a very high investment in inventory screens and frames. Further, it required skilled screen designers using great care and careful operators to assure proper positioning of the silk screens to avoid an unreasonably high number of rejected final products.
Another process used for direct numeral printing on such garments is referred to as the die cut process. In this process, a paper sheet is employed for each numeral image to be printed which is discarded after a single use. Each new die cut sheet must be replaced in a fixed frame manually.
Those skilled in the art have failed to find a satisfactory solution to these long recognized disadvantages, therefore volume manufactureres have been required to continue to use these old and well-known cumbersome processes to print numeral indicia on such garments using the prior conventional printing apparatus.